Cs620 clutch or chain problem?

[mojoe]

Hello, im a long time reader, first time posting new member from the st. Louis, mo area. I have read a lot and gained a lot of knowledge from this site and i greatly appreciate it. I recently have re acquired the CAD and purchased an echo 620p to add to the growing collection. I put on a tsumara 24" lightweight bar along with an oregon EXL 84DL chain and tensioned correctly, held bar up while tightening nuts. While spinning chain by hand i have tight and loose spots(3/16" of sag). This is the first time i have had this happen. After reading through numerous threads, i have checked everything suggested including measuring bar sprocket and rim sprockets and burs on the chain. Everything is matched 3/8 .050. One thing i found when turning the clutch drum by hand was it appears to be slightly oblong as i can see the gap get slightly smaller against the brake band. While spinning with a straight edge against the rim itself the rim spin true. I know this is not the ideal way to measure that but its what i have.
My questions are, is it normal for a clutch drum to be slightly out of round while the rim spins true? and is it possible that this could just be a chain problem? Should i just run it and see if the chain stretches out evenly? I am going to pick up a stihl chain to try to rule out the chain.

I also pulled an ms462 i bought recently out of the box and the drum on it doesnt look absolutely perfect while spinning slowly either. Maybe ive just never paid attention to this on other saws in the past. I appreciate any and all advice, or some friendly bashing if i have missed something in all the info i have been reading through.

 

[Duane(Pa)]

What you are seeing is not uncommon in my experience. Adjust so it’s tight, loose, tight, not tight, too tight, tight.

 

[mojoe]

Thanks, i suppose thats what i will do and hope everything wears in evenly. Here are some pictures, not the best, but not sure if that looks severe to you guys or nothing to worry about.

 

[atpchas]

If the pictures showing (1) 1/8" or more of sag at bottom of bar and (2) chain snug to bar are what you see when just rotating the chain, you definitely have a problem. That is not normal by any means. Finding the problem source is harder to tell from those pictures.
Do you have a different rim to swap in? If not, get one - you'll need it eventually anyway.
Did you buy from a local dealer? If so, let him figure it out.

 

[pioneerguy600]

If the pictures showing (1) 1/8" or more of sag at bottom of bar and (2) chain snug to bar are what you see when just rotating the chain, you definitely have a problem. That is not normal by any means. Finding the problem source is harder to tell from those pictures.
Do you have a different rim to swap in? If not, get one - you'll need it eventually anyway.
Did you buy from a local dealer? If so, let him figure it out.

These sort of chain tight then loose is usually related to the rim drive sprocket. Most often they are machined off center and therefor cause this tight then loose condition.

 

[pioneerguy600]

It only takes a little bit of off centering to cause the tight to loose slop in the chain, I have heard of at least one rim where the machining of the pockets where the drivers run that were not cut down deep enough so the drive teeth were bottoming out on one side thus causing the same condition.

 

[mojoe]

I appreciate the replies. This morning I ordered a new rim to try, hopefully it is as easy as that.
That saw i purchased from baileys, as the one i ordered from a local dealer last year still has not come in yet. Naturally after i pulled this saw out of the box i instantly trimmed limiter caps and did a mild muffler mod so im not sure if any dealer would warranty anything anyway. My fault for not putting bar and chain on first to check for the problem im seeing. Lesson learned.

 

[pioneerguy600]

I appreciate the replies. This morning I ordered a new rim to try, hopefully it is as easy as that.
That saw i purchased from baileys, as the one i ordered from a local dealer last year still has not come in yet. Naturally after i pulled this saw out of the box i instantly trimmed limiter caps and did a mild muffler mod so im not sure if any dealer would warranty anything anyway. My fault for not putting bar and chain on first to check for the problem im seeing. Lesson learned.

If you have time and want to visually see what the rim and chain is doing just remave the clutch cover and put some big thick washers on over the studs, then inatall the nuts down on the washers, pull the bar out til the chain is tight and tighten the nuts. Try pulling the chain around by hand, have gloves on or pad the chain where you grab it, you can watch what the chain is doing then.

 

[mojoe]

New rim came in today so i put that on, with the oregon exl chain on, it took out some sag but not all, with the stihl chain there was no change at all, not sure why the difference between chain brands. I also tried a 20" bar and oregon chain and it had same problem. I spent a couple hours marking the bar, chain links and clutch drum and turning by hand trying to make it obvious where the problem is, It does seem to relate more to the revolutions of the drum vs the bar sprocket. I left the shop in a hurry and forgot to grab extra bar nuts and washers to try what pioneerguy recommended. Tomorrow i am going to try swapping my 590 clutch drum onto the 620 to try to rule something else out. Other than a possible bent crank am i overlooking anything?

 

[pioneerguy600]

The crank would have to be bent severely to cause that much movement, its usually one of the add on units like the rim drive, possibly the clutch drum machined off center or a bad bearing, broken apart, needles bunched up to one side.

 

[POGuy]

Maybe both the rim sprocket AND clutch drum are BOTH out of round and aligned at the worst point of out of round. Maybe try rotating the rim sprocket fwd to the next point while keeping drum stationary till 180 degrees apart from starting mount?

 

[KASH]

Last week I was putting a Stihl bar on a 041 and the chain would turn loose but bind when tight .After putting it on and off a half dozen times I carefuly checked the groove of the bar .
I found a small piece of metal jammed in the rail right at the tail of the bar you could not see it jamming because it was behind the cover plate.When I examined the SPT I could see were the piece was broken off.
Kash

 

[Rooshooter]

While spinning chain by hand i have tight and loose spots(3/16" of sag). This is the first time i have had this happen. After reading through numerous threads, i have checked everything suggested including measuring bar sprocket and rim sprockets and burs on the chain. Everything is matched 3/8 .050. One thing i found when turning the clutch drum by hand was it appears to be slightly oblong as i can see the gap get slightly smaller against the brake band. While spinning with a straight edge against the rim itself the rim spin true. I know this is not the ideal way to measure that but its what i have.

I have come across this problem many times, I think you will find that the rim sprocket is out of round. This is noticeable on Chinese manufactured rims which are manufactured in a process called investment casting, also the rim is not machined on the outer edge, I have measured up to .030" out of round on this crap.
I spoke to one wholesale supplier who told me that to have the Chinese rims machined would double their cost " WHICH WOULD GO FROM 45¢ to 90¢ " This is why when you buy cheap you buy twice.

 

[POGuy]

I have come across this problem many times, I think you will find that the rim sprocket is out of round. This is noticeable on Chinese manufactured rims which are manufactured in a process called investment casting, also the rim is not machined on the outer edge, I have measured up to .030" out of round on this crap.
I spoke to one wholesale supplier who told me that to have the Chinese rims machined would double their cost " WHICH WOULD GO FROM 45¢ to 90¢ " This is why when you buy cheap you buy twice.

Good catch, never would have believed someone would manufacture something so poorly knowing it potentially has to spin at 13,000 rpm

 

[mojoe]

So far i have tried 3 new oregon rims and a new stihl rim. Tried 3 bars so far, 2 new and 1 well used with 6 different chains, all but one was new. Swapped the cluth drum from my 590 onto the 620. Nothing seemed to help. I will try to do some measuring with a caliper on the rims i have to see if i have just been unlucky and will check the bar again for any obstructions in the groove. Thanks for the info and help.

 

[Cliff R]

Time to check the end of the crankshaft to see how much run-out it has.........

 

[mojoe]

So, the other 620p i had ordered last year finally came in. I put the bar and chain on and wouldn't you know it has the same problem but slightly worse. This is aggravating. Would be hard to believe i got 2 saws with excessive crank runout right out of the box. The clutch drum looks even more out of round than the first one, so im leaning towards that being the problem. One saw is dated june 21 and the other july 21. Maybe the drums came from the same batch. I took my stihl 462 out the box again to double check and its clutch drum appears to spin much more true than these 620s, not perfect but not near as bad. as does my well used 261, echo cs450 and 590.
Does anyone else have a june/july of 21 620 that presents the same issue?

Im thinking of buying a clutch drum of a different manufacturer to try out, is chinese my only option or does anyone know if there is a drum that will work from another saw manufacturer and not made by oregon?

 

[Fatherwheels]

I appreciate the replies. This morning I ordered a new rim to try, hopefully it is as easy as that.
That saw i purchased from baileys, as the one i ordered from a local dealer last year still has not come in yet. Naturally after i pulled this saw out of the box i instantly trimmed limiter caps and did a mild muffler mod so im not sure if any dealer would warranty anything anyway. My fault for not putting bar and chain on first to check for the problem im seeing. Lesson learned.

Looks like a new saw, they have a 5 yr warrant for non commercial use,
take it in and show the dealer how its tight then loose, you should be offered
a new part, it could be the clutch drum is off center, it could be the rim drive is
off center, worst case, mark clutch drum with a permanent marker, mark rim
drive as well, and rotate one tooth at a time to see if it improves the overall situation.
I hate it when a saw comes like this, I now make dam sure to rotate the chain prior to
purchase, as it can be a nightmare to go back afterwards to complain. I had one saw
like this, sold it, learned to now check things before putting down the money, especially
if it turns out the crank is not true as that is a major issue to solve.

 

[Fatherwheels]

So far i have tried 3 new oregon rims and a new stihl rim. Tried 3 bars so far, 2 new and 1 well used with 6 different chains, all but one was new. Swapped the cluth drum from my 590 onto the 620. Nothing seemed to help. I will try to do some measuring with a caliper on the rims i have to see if i have just been unlucky and will check the bar again for any obstructions in the groove. Thanks for the info and help.

Bar will not be the issue, it has no way to get longer then shorter,
the crank though has, if its not true. Make sure the clutch bearing is ok
too, though I doubt it would result in your issue.

 

[Fatherwheels]

So, the other 620p i had ordered last year finally came in. I put the bar and chain on and wouldn't you know it has the same problem but slightly worse. This is aggravating. Would be hard to believe i got 2 saws with excessive crank runout right out of the box. The clutch drum looks even more out of round than the first one, so im leaning towards that being the problem. One saw is dated june 21 and the other july 21. Maybe the drums came from the same batch. I took my stihl 462 out the box again to double check and its clutch drum appears to spin much more true than these 620s, not perfect but not near as bad. as does my well used 261, echo cs450 and 590.
Does anyone else have a june/july of 21 620 that presents the same issue?

Im thinking of buying a clutch drum of a different manufacturer to try out, is chinese my only option or does anyone know if there is a drum that will work from another saw manufacturer and not made by oregon?

Sadly I think if you got one, there is every chance you could get another, a machine
with the wrong settngs dialed in, thats all it takes, might go unnoticed until complaints
start coming in from dealers or distributors.
I would return it as unfit for purpose, one can only take so much crap.
My very first 501 had a little run out, I sold it, it would drive me nuts knowing
this was going on.